This invention relates to the cloning of the gene for Charcot-Leyden crystal protein.
Charcot-Leyden crystals (CLC), first described in 1853 by Charcot and Robin in the spleen and blood of a patient who died of leukemia (Charcot and Robin, C. R. Mem. Soc. Biol. 5:44, 1853), and later by Leyden in the sputum of asthmatics (Leyden, Arch. Pathol. Anat. 54:324, 1872), are distinctive hexagonal, bipyramidal crystals that are classically observed in tissues and secretions from sites of eosinophil-associated inflammatory reactions that include those of asthma and myeloid leukemias, as well as allergic, parasitic, and other diseases (Beeson and Bass, The Eosinophil, In Problems in Internal Medicine (Smith, ed), Philadelphia: W. B. Saunders 14:39-42, 1977; Ottesen and Cohen, Allergy: Principles and Practice (Middleton et al., ed.), St. Louis: C. V. Mosby 2:584-632, 1978). Although CLC are considered a hallmark of the eosinophil, basophils have also been shown to form CLC in vitro (Ackerman et al., J. Exp. Med. 155:1597, 1982) and in vivo (Dvorak and Ackerman, Lab. Invest. 60:557-567, 1989), and CLC have been identified within human basophil granules by ultrastructural studies (Dvorak and Ackerman, 1989).
Eosinophil CLC are formed by a single, markedly hydrophobic protein (CLCP) of 17,400 daltons (Gleich et al., J. Clin Invest. 57:633-640, 1976; Ackerman et al., J. Immunol. 125:2118-2126, 1980; Weller et al., J. Biol. Chem. 259:15100-15105, 1984) that exhibits lysophospholipase activity (lysolecithin acylhydrolase), catalyzing the deacylation of a single fatty acid from lysophospholipids (Weller et al, J. Biol. Chem. 259:15100-15105, 1984). Chromatographically purified human eosinophil lysophospholipase is immunochemically, physicochemically and enzymatically indistinguishable (identical Michaelis constants) from eosinophil CLCP (Weller et al., 1984), and crystallizes to form hexagonal, bipyramidal crystals of habit identical to CLC.
CLCP comprises the sole protein constituent of both native CLC formed in vivo and CLC prepared in vitro from disrupted eosinophils (Weller et al., J. Immunol. 128:1346-1349, 1982). At .about.8.5 pg/cell in eosinophils and 4-6 pg/cell in basophils, CLCP is one of the most prominent constituents of each of these cell types. Ultrastructurally, CLCP has been localized in both the eosinophil and basophil to granule compartments; in the mature eosinophil, CLCP was localized to a large, crystalloid-free "primary" granule population (Dvorak et al., Blood 72:150-158, 1988), while in the basophil, CLCP has been found to be a constituent of the histamine, chondroitin sulfate containing basophil granule (Dvorak and Ackerman, Lab. Invest. 60:557-567, 1989). However, quantitative considerations, measurements of enzyme activity of intact cells, and localization by light microscopy using indirect immunofluorescence suggest additional plasma membrane, nuclear membrane or cytoplasmic sources.
Although CLCP comprises 7-10 percent of total eosinophil cellular protein and possesses lysophospholipase activity, its role in eosinophil and basophil function remains obscure.